1. Field of the Invention
This invention relates to a tilting type steering apparatus in which a steering column of an automotive steering apparatus is supported in such a manner as to be freely rockable relative to a vehicle body.
2. Related Background Art
An apparatus for adjusting the height of a steering wheel, called "tilting type steering apparatus" has been conventionally known in which the steering wheel has been constructed so that its height can be adapted to a driver's physical constitution, driving posture, etc.
As such a tilting type steering apparatus, one disclosed in U.S. Pat. No. 4,594,909 has been known so far.
The tilting type steering apparatus disclosed in this patent is called an "oscillating type". In this apparatus an articulated steering shaft 1 is allowed to pass through, as shown in FIG. 3, a steering column 2 formed in a cylindrical form and divided into two parts: a lower steering column 3 and an upper steering column 4, and both steering columns 3 and 4 are connected with each other a supporting bracket 5 portion mounted to the vehicle body. Also the upper steering column 4 is freely rockable around a first horizontal axis an pivots 6, 6 provided at the supporting bracket 5 as shown in FIGS. 4 to 6.
Between the supporting bracket 5 and the upper steering column 4, a locking mechanism is provided which can be freely engaged and disengaged by a tilt lever 7 for rocking around the first horizontal axis so that the upper steering column 4 may be connected with the supporting bracket 5 (rocking of the upper steering column 4 is made impossible), or be made to be freely displaceable relative to the supporting bracket 5 (rocking of the upper steering column 4 is made possible).
That is, at the under surface, etc. of a dash board 8, one end of the upper steering column 4 is pivotally supported at the supporting bracket 5 by pivots 6, 6 provided at the supporting bracket 5 fixed to the vehicle body. At the under surface of the upper steering column 4, a first engaging member 9 is fixed. At the under surface of the first engaging member 9, a circular convex surface is centered around the first horizontal axis, defined by pivots 6, 6, at the under surface of which first gear teeth 10 are formed.
A horizontal shaft 11 is mounted the supporting bracket 5, and one end (the left end in FIGS. 4 and 6) of a second engaging member 12 for engaging or disengaging the first engaging member 9 with rocking of the tilt lever 7 is supported by shaft 11 for pivotal movement about the shaft axis. At the top edge (top edge of the right end in FIG. 4) of the other end of this second engaging member 12, second gear teeth 13 are formed which can freely engage or disengage the first teeth 10 formed at the under surface of the first engaging member 9.
At a shaft 14 provided to span over between the lower ends of the tilt lever 7 a roller 15 is mounted to allow the top surface of the roller 15 to abut on the under surface of the second engaging member 12.
A pin 18 projecting from the side of the second engaging member 12 engages an inclined long hole 17 formed in a rocking plate 16 fixed to the tilt lever 7.
When the tilt lever 7 is rocked counterclockwise in FIG. 4, the roller 15 retreats from a position below the other end (the right end in FIG. 4) of the second engaging member 12, and at the same time, the other end of the second engaging member 12 displaces downward due to the engagement between the inclined long hole 17 and the pin 18 because of the above-mentioned construction.
As a result, the engagement is released between the second teeth 13 formed at the top edge of the other end of the second engaging member 12 and the first teeth 10 formed at the under surface of the first engaging member 9 fixed at the under surface of the upper steering column 4. Thus the upper steering column 4 can freely rock around the first horizontal axis at pivots 6, 6 (within a range in which a pin 19 projecting from the side of the upper steering column 4 can move inside a long hole 20 formed in the supporting bracket 5), enabling the free adjustment of the height of the steering wheel fixed to the one end of the steering shaft 1 passing through the inside of the upper steering column 4.
When the tilt lever 7 is rocked clockwise in FIG. 4 after thus adjusting the height of the steering wheel, the roller 15 enters below the other end of the second engaging member 12, and presses upward the other end of the second engaging member 12 to cause the second teeth 13 the second teeth 13 engage the newly confronting first teeth 10 (i.e., the teeth 10 which confront the second teeth 13 at the adjusted position of the upper steering column 4). This prevents the upper steering column 4 from rotating around the first horizontal axis at 6, 6.
As a result, the steering wheel is maintained at the adjusted height. Since the tilt lever 7 is given an elastic force to rock clockwise in FIG. 4 by a tensile spring 21 in this state, the roller 15 does not inadvertently retreat from below the second engaging member 12.
In the case of the foregoing construction, the first engaging member 9 is fixed to the under surface of the upper steering column 4, and the second engaging member 12 is pivotally supported on the supporting bracket 5. However, it is also possible to fix the first engaging member 9 to the under surface of the supporting bracket 5 and pivotally support the second engaging member 12 on the upper steering column 4 as shown in FIG. 7.
In the case of such conventional tilting type steering apparatus as constructed and used as mentioned above, when a strong force in the vertical direction is applied to the steering column 4, the roller 15 mounted to the shaft 14 displaces to the right in FIG. 4 or to the left in FIG. 7 against an elastic force of the tensile spring 21 to release the engagement between the first and the second gear teeth 10 and 13, causing the steering column 4 to displace.
That is, when a strong force in the vertical direction is applied to the steering column 4, the second engaging member 12 is pressed clockwise in FIG. 4 or counterclockwise in FIG. 7 as a reaction of a pressing force exerting on the engaged surface between the first and the second engaging teeth 10 and 13, and the tilt lever 7 displaces counterclockwise in FIG. 4 or clockwise in FIG. 7 by the engagement between the under surface of the second engaging member 12 and the roller 15. As a result, the engagement between the first and the second engaging teeth 10 and 13 is released as mentioned above, causing the steering column 4 to displace.
To prevent the displacement of the steering column 4, it is conceivable to strengthen the elastic force of the tensile spring 21. In this case, a force required to pivot the tilt lever 7 will be great when adjusting the height of the steering wheel so as to impair the operability. Accordingly this is not desirable.